Trends and drivers of soil multifunctionality along elevation gradients in the Altun Shan drylands of China

This study was conducted to analyze the variation of soil multifunctionality(SMF) along elevation and the driving factors in the Altun Shan.Soil samples(0–10 cm) were collected from 15 sites(H01 to H15) at every 200 m elevation interval,covering a total range from 900 m to 3500 m above mean sea level. We investigated climate factors(mean annual temperature, MAT; mean annual precipitation,MAP), soil environment(soil water content, electrical conductance, and pH), vegetation factors, and elevation to determine which of them are the main driving factors of the spatial variability of SMF in the Altun Shan. We explored the best-fit model of SMF along the changes in elevation using a structural equation model, performed variance partitioning analysis(VPA) on SMF with the “varpart” function to explain the relative contribution of various environmental factors to SMF changes, and used a random forest model for relative importance analysis.The results showed that SMF in the Altun Shan significantly increased with elevation in a linear trend.The main driver of changes in SMF was found to be MAP. Although the rise in elevation did not have a significant direct effect on changes in SMF, it could indirectly affect SMF by significantly influencing MAP,p H, MAT, and normalized difference vegetation index(NDVI). When considering climate, soil environment,and vegetation factors together, they explained 76% of the variation in SMF. The largest contribution to the variation in SMF was attributed to the independent effect of climate(0.31) and its interactive effect with soil(0.30). The relative importance of MAP on SMF changes was found to be the greatest. It is indicated that changes in SMF are caused by the combined effect of multiple environmental conditions. These findings are essential for understanding the spatial variability and drivers of SMF in dryland mountain ecosystems, especially concerning the function of mountain ecosystems in the context of global climatic changes.